ARDS was first described in 1967, and its modern definition is the result of decades of international collaboration and refinement.1 It is characterised by acute onset inflammation and bilateral pulmonary infiltrates not fully explained by cardiac failure or fluid overload. It may be a consequence of both pulmonary and non-pulmonary primary pathologies and therefore occurs in a wide patient population. The Berlin criteria enable both diagnosis and classification of severity based on the extent of hypoxaemia (PaO2 : FiO2 ratio); mild, moderate and severe ARDS correspond with a mortality of 27%, 32% and 45%, respectively.2
